Recently, the ink-jet recording method has been applied to various printing fields such as photography, various kinds of printings, and special printings such as marking and color filters because the ink-jet recording method can produce an image simply and at low cost.
Particularly, an image quality almost equal to a silver halide photograph can be obtained by the following means: a recorder which enables to jet and to control a fine dot; an ink having improved properties of color reproduction area, durability, and jetting property; and an exclusive paper in which the absorptivity of the ink, coloring property of the coloring material, surface glossiness are greatly increased.
The improvement of the image quality of today's ink-jet recording method is attained only when all of the recorder, ink, and the exclusive paper are get together.
However, for the ink-jet system which requires exclusive papers, the limitation of the recording material and the cost increase of the recording material become a problem. Accordingly, many trials have been made to record onto the recording material different from the exclusive paper using the ink-jet method. They are, for example, a phase change ink-jet system using a solid wax ink at a room temperature, a solvent type ink-jet system using a quick dry type organic solvent as a main component, or a UV ink-jet system in which a cross-linkage is formed by an ultraviolet (UV) ray after recording.
An actinic radiation curable composition which is cured with an active energy radiation such as a ultraviolet ray and an electron beam, is put in practical use of various applications, such as coating materials (for a plastic, a paper, a woodwork and an inorganic material), an adhesive agent, a printing ink, a print circuit board and an electric insulation. And as an ink-jet ink system which uses these polymerizable compositions, an ultraviolet ray curable ink-jet ink which is hardened by an ultraviolet ray is well known. The ink-jet recording method using the ultraviolet ray curable ink has been attracting attention in recent years from the point that it dries quickly and it can perform recording to a recording material having no ink absorptivity.
Moreover, there were introduced attempts for forming an image on various recording materials by using a mechanism in which a first ejected liquid and the subsequently ejected liquid are allowed to react to result in aggregation of a colorant (for example, refer to patent documents 1). However, it is hard to obtain a glossy image using this composition because the image is produced by the aggregated colorant. Furthermore, there was disclosed a method for forming an image using an aqueous ultraviolet ray curable ink (for example, refer to patent documents 2). However, when the aqueous ultraviolet ray curable ink was used, the hardening property (drying characteristics) of the first ejected ink became insufficient at the time of the reaching of the later ejected ink on the target of the hardened membrane (polymerized film), and there were problems, such as inferior adhesion of the liquids.
Moreover, there was introduced another image forming method, in which an actinic radiation curable ink containing a photoinitiator and a photo-polymerizable compound but containing no colorant (or containing substantially no colorant) was coated on an entire surface of a recording material including non-image forming area with a roll coater or was applied with an ink-jet method prior to applying an ink containing a colorant on the recording material. Subsequently, the applied actinic radiation curable ink was semi-cured by irradiation with actinic radiations, then the ink containing a colorant was ejected on the semi-cured first ink to form a an image (for example, refer to patent document 3). By this image formation method, since the degree of curing tends to change depending on the effect of the recording environment (temperature and humidity) or on the difference of the amount of inks which form each image, it is difficult to reproduce a semi-cured condition with high repeatability, and, as a result, a high-definition image cannot be created.
In addition, as the same image forming method as described in the patent document 3, the following patent documents can be cited: Japanese patent application publication open to public inspection (JP-A) Nos. 2008-105382, 2008-23980, 2008-105378, 2008-105379 and 2008-100501.
There was introduced another image forming method in which an actinic radiation curable ink containing no colorant (but containing a photoinitiator and a photo-polymerizable compound) was imagewise ejected on the recording material prior to ejecting an ink containing a colorant, then, without applying an actinic radiation, the ink containing a colorant was ejected (for example, refer to patent document 4). In this image forming method, deterioration of an image caused by coalescence of adjacent dots which may be a problem during high-speed printing cannot be fully inhibited. As a result, it is hard to form a high-definition image. Especially, when an image is formed with very minute ink droplets of 0.1 to 4.0 pl, the deterioration of an image caused by coalescence of adjacent dots will become significant.
In addition, as the same image forming method as described in the patent document 4, the following patent documents can be cited: JP-A Nos. 2008-105254, 2007-313839, 2007-314734, 2007-254560, 2007-237405 and 2007-231206.
There was introduced an image forming method in which a first actinic radiation curable ink (containing a photoinitiator and a polymerizable compound) without substantially containing no colorant is ejected on a recording material, and then it is cured by irradiation with actinic rays. Subsequently, a second ink containing a colorant is ejected on the cured first ink. And again, the image is cured and fixed by irradiation with actinic rays (for example, refer to patent document 5). With this image forming method, deterioration of an image caused by coalescence of adjacent dots which may be a problem during high-speed printing cannot be fully inhibited. As a result, it is hard to form a high-definition image.
Patent Document 1: Japanese Patent Application Publication open to public inspection (JP-A) No. 2001-115067
Patent Document 2: JP-A No. 2000-186243
Patent Document 3: JP-A No. 2008-105387
Patent Document 4: JP-A No. 2008-105253
Patent Document 5: JP-A No. 2003-285546